By August, Arizona Democratic Rep. Ann Kirkpatrick had raised more than $1.4 million for her campaign. Her opponent, Paul Gosar, had raised just $410,000 and spent all but $41,000 of it after his primary.

Should be a slam-dunk for Kirkpatrick, right? Not this year.

Gosar doesn’t have to worry about his fundraising gap thanks to the 60 Plus Association, Americans for Prosperity and its companion foundation, which are in line to drop a combined $1 million into his effort to oust the incumbent freshman.

That helps explain why Kirkpatrick is one of a dozen Democrats whom the nonpartisan Cook Political Report recently shifted from the its ranks of highly endangered incumbents to the walking dead.

In nearly all of those districts, a flood of outside dollars is being aimed at vulnerable incumbents to bolster the spending of their challengers and the official Republican Party machinery. And while outside groups have long had a role during campaign seasons, the sheer volume of spending this cycle risks drowning out the candidates.

According to Democratic National Committee strategist David Plouffe, spending by outside interest groups through August was double the amount spent by Republican and Democratic candidates combined.

This Friday is the deadline for third-quarter reports for candidates, and those records will shed substantially more light on whether Republican challengers are enjoying late infusions of cash that could make the outside spending less necessary — or turn it into overkill.

But, based on the figures available from earlier in the cycle, many of the GOP challengers alone would not have had the financial muscle to prompt the Cook Report to nearly write off the candidacies of a dozen incumbents.

David Wasserman, author of the Cook House report, explained in his introduction that he changed the rankings in part because of negative poll numbers for the incumbents.

In the case of Kirkpatrick’s reelection campaign, she seems to be a victim of friendly fire.

Her numbers slumped after the Obama administration challenged Arizona’s tough new immigration law. Kirkpatrick had expressed her objections to the legislation but had managed to keep it from becoming a major issue in her northern Arizona race.

But when her weakened poll numbers came to light, Republicans and conservative groups moved in for the kill — sprinting right past Gosar, the cash-strapped Republican who was nominated to compete against her.

In the past month, Kirkpatrick spent about $340,000 on advertising and received about $88,000 in support from the Democratic Congressional Campaign Committee, for a combined ad budget of roughly $426,000.

During that same period, the National Republican Congressional Committee dropped $304,350 into the race, and the 60 Plus Association added an additional $295,000 in attack ads, for an anti-Kirkpatrick campaign that’s cost nearly $600,000, according to Kantar Media/CMAG, a private firm that tracks political advertising.

The amount of spending on advertising in the past month by Kirkpatrick’s actual opponent, local dentist Gosar: zero.

The 60 Plus Association is one of several groups playing big roles in the 2010 cycle. It presents itself as a conservative alternative to AARP but has been accused of being a front group for big drugmakers.

The third group expected to weigh in on the Kirkpatrick fight is Americans for Prosperity, an organization financed by conservative billionaire David Koch and Richard Fink, a member of the board of directors of Koch Industries.

Those two groups and the U.S. Chamber of Commerce are also combining forces in Florida, where Democratic Rep. Suzanne Kosmas is under fire. Her ranking by Cook has moved from embattled-but-competitive incumbent to likely loser.

As of August, Kosmas had raised nearly $2 million for her campaign and had three-quarters of it still in the bank. Her Republican opponent, Sandy Adams, had raised $390,000 and spent all but about $115,000.

But the ad trackers at the DCCC have identified nearly $1.6 million in spending that could flow from the trio of outside groups to match or surpass the incumbent’s advertising spending, which amounts to $736,000 so far.

Much of that money has yet to be spent.

In the past month, the NRCC has dropped $162,000 in the race, but the Chamber has invested only about $80,000.

Still, David Levinthal of the nonpartisan Center for Responsive Politics, which is also tracking the independent expenditures, said that shouldn’t be viewed as good news by Kosmas’s camp.

“We are seeing organizations dropping six figures, seven figures in a single day,” said Levinthal. “There still is plenty of time for them to get involved, if they are pledging to do that but haven’t yet.”

That’s a warning that should sound alarms for all of the downgraded Democrats who are being swamped, or soon will be, by the outside players.

Among them is Colorado’s Betsy Markey, a conservative freshman whose vote switch on health care reform immediately put her in the GOP’s cross hairs.

Markey is facing a well-financed opponent. As of July, Markey had raised $2.2 million and had $1.5 million in the bank, compared with Republican Cory Gardner’s $1.3 million raised and $735,000 in cash.

But that hasn’t stopped the Chamber and Americans for Prosperity from pledging to spend more than $650,000 on ads advocating her defeat. Markey is also being attacked by the NRCC, which has already spent more than $400,000 to send her packing.

Unlike some of her colleagues, at least Markey doesn’t have to walk through the political shadow land alone. A myriad of pro-Democratic groups, including a couple of labor unions, are rallying to respond to the Republican spending.

Women Vote, an organization formed by EMILY’s List, has been on the air in Colorado for the past month, sinking $456,500 into Markey’s quest to save her seat.

And last week, Markey acquired the endorsement of another unusual Democratic ally: the National Rifle Association.

The NRA nod may not come with boatloads of high-profile advertising, but its low-key candidate endorsement sheet, sent out to members by snail mail, has been known to make a difference if a race is close.